A technique is proposed for the development of a real-time, 3- dimensional ultrasound-based visualization and implant system with robotic augmentation for intraoperative dose planning, real-time robotic guidance of radioactive implants and on-line implant assessment during the procedure for treatment of prostate cancer. This new system includes a real-time 3-dimensional endorectal imaging probe and supporting visualization interfaces coupled with robotic insertion of needles/sources in exact concurrence with optional dosimetry plan. Present techniques using transrectal ultrasound guidance for brachytherapy are difficult to implement and often result in unacceptable rates of complication. The aim of the proposed technique is to consolidate the total implant procedure, reduce Complication rates and improve local control by linking real-time intraoperative dosimetry with robotic-assisted source implantation during 3D ultrasound-guided brachytherapy. The primary objective of Phase I is to establish feasibility of robotic needle/seed implantation in phantoms and determine achievable levels of accuracy. PROPOSED COMMERCIAL APPLICATIONS: The outcome of this research could be of immediate benefit in the treatment of prostate cancer using higher dose radiation with more accurate localization and fewer toxicities1less morbidity. It would provide the ability to visualize in real time the 3D prostate volume during robotic placement of implants, providing implants which reflect optimal dosimetry even in the hands of less experienced clinicians. A large group of patients with early-stage disease are candidates, including patients which would have normally been excluded because of public arch interference.